Fig. 2.
Localization accuracy (signed error between response and target location) in Az for multi-sampled targets in the horizontal plane (0° El) for Young (a), Middle-aged (b), and Elderly (c) subjects for the target fixation paradigm, and the Ctr, L20° and R20° sustained fixation paradigm. Data points are offset slightly in Az for graphic clarity. The slope of accuracy vs. target location is related to spatial gain (SG = slope ? 1.0, where 1.0 represents perfect performance). All age groups demonstrated comparable overshoot (Az SG > 1.0, or a positive slope as shown here) during target fixation. However, the overshoot is reduced significantly with Ctr fixation in the Young and the Middle-aged, but not in the Elderly. Eccentric fixation (L and R 20°) predominantly shifts perceived target Az in the direction of gaze across space